With approximately 96% of precincts reporting by early Wednesday morning, Flake, the heavy favorite, had received 69% of the votes to Cardon's 21%, the unofficial results showed.

"Congratulations to Congressman Jeff Flake," Cardon wrote on his Facebook page. "It was a long, tough race. Now it's time to elect Mitt Romney as our next President and give him the Republican Senate our nation needs."

Two other candidates were far behind the prominent pair.

Despite being outraised by his opponent, Flake, a six-term congressman, saw strong backing from both establishment and tea party Republicans in his quest to win the open seat soon to be vacated by retiring Senate Minority Whip Jon Kyl.

His challenger, however, put up a tough fight. A political newcomer, Cardon has not previously held public office and runs his family's real estate investment firm, the Cardon Group.

He took in a considerable amount of money this cycle - $9.6 million as of August 8 –but about 90% of his campaign war chest came from his own pocket, according to reports filed with the Federal Election Commission.

Flake, meanwhile, raised $5.4 million but has lent no money to his campaign. He also had the support of both Kyl and Arizona's senior senator, John McCain. Flake, known as a maverick, was a major backer of McCain early on in the senator's 2008 presidential bid.

The congressman also fell in the column of one of the few national politicians whom former Alaska Gov. Sarah Palin endorsed in a Senate race this cycle. While Cardon painted himself as the tea party favorite in the race, Palin backed Flake in July, saying the congressman has led a tough fight against "pork barrel spending."

"He's not afraid to 'go rogue' against his own party and its leadership," she wrote in her endorsement announcement.

Flake will face former U.S. Surgeon General Richard Carmona, who did not undergo a competitive Democratic primary battle.